text: 
  //
  // This source file is part of appleseed.
  // Visit https://appleseedhq.net/ for additional information and resources.
  //
  // This software is released under the MIT license.
  //
  // Copyright (c) 2010-2013 Francois Beaune, Jupiter Jazz Limited
  // Copyright (c) 2014-2018 Francois Beaune, The appleseedhq Organization
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  //
  
  // Interface header.
  #include "genericsamplegenerator.h"
  
  // appleseed.renderer headers.
  #include "renderer/global/globaltypes.h"
  #include "renderer/kernel/aov/aovaccumulator.h"
  #include "renderer/kernel/rendering/isamplerenderer.h"
  #include "renderer/kernel/rendering/localsampleaccumulationbuffer.h"
  #include "renderer/kernel/rendering/pixelcontext.h"
  #include "renderer/kernel/rendering/sample.h"
  #include "renderer/kernel/rendering/samplegeneratorbase.h"
  #include "renderer/kernel/shading/shadingresult.h"
  #include "renderer/modeling/frame/frame.h"
  #include "renderer/utility/settingsparsing.h"
  
  // appleseed.foundation headers.
  #include "foundation/image/canvasproperties.h"
  #include "foundation/image/image.h"
  #include "foundation/math/filtersamplingtable.h"
  #include "foundation/math/population.h"
  #include "foundation/math/qmc.h"
  #include "foundation/math/scalar.h"
  #include "foundation/math/vector.h"
  #include "foundation/utility/autoreleaseptr.h"
  #include "foundation/utility/statistics.h"
  
  // Standard headers.
  #include <cassert>
  #include <cstdint>
  #include <vector>
  
  using namespace foundation;
  
  namespace renderer
  {
  
  namespace
  {
      class GenericSampleGenerator
        : public SampleGeneratorBase
      {
        public:
          GenericSampleGenerator(
              const Frame&                    frame,
              ISampleRendererFactory*         sample_renderer_factory,
              const ParamArray&               params,
              const size_t                    generator_index,
              const size_t                    generator_count)
            : SampleGeneratorBase(generator_index, generator_count)
            , m_params(params)
            , m_canvas_width(frame.image().properties().m_canvas_width)
            , m_canvas_height(frame.image().properties().m_canvas_height)
            , m_window_origin_x(static_cast<int>(frame.get_crop_window().min.x))
            , m_window_origin_y(static_cast<int>(frame.get_crop_window().min.y))
            , m_window_width(static_cast<int>(frame.get_crop_window().extent()[0]))
            , m_window_height(static_cast<int>(frame.get_crop_window().extent()[1]))
            , m_sample_renderer(sample_renderer_factory->create(generator_index))
            , m_window_width_next_pow2(next_power(static_cast<double>(m_window_width), 2.0))
            , m_window_height_next_pow3(next_power(static_cast<double>(m_window_height), 3.0))
            , m_filter_sampling_table(frame.get_filter_sampling_table())
          {
          }
  
          void release() override
          {
              delete this;
          }
  
          void print_settings() const override
          {
              m_sample_renderer->print_settings();
          }
  
          void reset() override
          {
              SampleGeneratorBase::reset();
              m_rng = SamplingContext::RNGType();
          }
  
          StatisticsVector get_statistics() const override
          {
              Statistics stats;
              stats.insert("max sampling dimension", m_total_sampling_dim);
  
              StatisticsVector vec;
              vec.insert("generic sample generator statistics", stats);
              vec.merge(m_sample_renderer->get_statistics());
  
              return vec;
          }
  
        private:
          struct Parameters
          {
              const SamplingContext::Mode     m_sampling_mode;
  
              explicit Parameters(const ParamArray& params)
                : m_sampling_mode(get_sampling_context_mode(params))
              {
              }
          };
  
          const Parameters                    m_params;
          const size_t                        m_canvas_width;
          const size_t                        m_canvas_height;
          const int                           m_window_origin_x;
          const int                           m_window_origin_y;
          const int                           m_window_width;
          const int                           m_window_height;
          auto_release_ptr<ISampleRenderer>   m_sample_renderer;
          SamplingContext::RNGType            m_rng;
  
          const double                        m_window_width_next_pow2;
          const double                        m_window_height_next_pow3;
  
          const FilterSamplingTable&          m_filter_sampling_table;
  
          Population<std::uint64_t>           m_total_sampling_dim;
  
          AOVAccumulatorContainer             m_aov_accumulators;
  
          size_t generate_samples(
              const size_t                    sequence_index,
              SampleVector&                   samples) override
          {
              // Compute the sample position in NDC.
              const size_t Bases[2] = { 2, 3 };
              const Vector2d s = halton_sequence<double, 2>(Bases, sequence_index);
  
              // Compute the coordinates of the pixel in the padded crop window.
              const Vector2d t(s[0] * m_window_width_next_pow2, s[1] * m_window_height_next_pow3);
              const int x = truncate<int>(t[0]);
              const int y = truncate<int>(t[1]);
  
              // Reject samples that fall outside the actual frame.
              if (x >= m_window_width || y >= m_window_height)
                  return 0;
  
              // Create a sampling context. We start with an initial dimension of 2,
              // corresponding to the Halton sequence used for the sample positions.
              SamplingContext sampling_context(
                  m_rng,
                  m_params.m_sampling_mode,
                  2,                          // number of dimensions
                  sequence_index,             // number of samples
                  sequence_index);            // initial instance number
  
              // Sample the pixel filter.
              sampling_context.split_in_place(2, 1);
              const Vector2f f = sampling_context.next2<Vector2f>();
              const Vector2d pf(
                  static_cast<double>(m_filter_sampling_table.sample(f.x)) + 0.5,
                  static_cast<double>(m_filter_sampling_table.sample(f.y)) + 0.5);
  
              // Transform the sample position back to NDC.
              const Vector2d sample_position(
                  (m_window_origin_x + x + pf[0]) / m_canvas_width,
                  (m_window_origin_y + y + pf[1]) / m_canvas_height);
  
              // Create a pixel context that identifies the pixel and sample currently being rendered.
              const PixelContext pixel_context(
                  Vector2i(m_window_origin_x + x, m_window_origin_y + y),
                  sample_position);
  
              // Render the sample.
              ShadingResult shading_result;
              m_sample_renderer->render_sample(
                  sampling_context,
                  pixel_context,
                  sample_position,
                  m_aov_accumulators,
                  shading_result);
  
              // Update sampling statistics.
              m_total_sampling_dim.insert(sampling_context.get_total_dimension());
  
              // Report then ignore invalid samples.
              if (!shading_result.is_valid())
              {
                  signal_invalid_sample();
                  return 0;
              }
  
              // Create a single sample.
              Sample sample;
              sample.m_pixel_coords = pixel_context.get_pixel_coords();
              sample.m_color = shading_result.m_main;
              samples.push_back(sample);
  
              return 1;
          }
      };
  }
  
  
  //
  // GenericSampleGeneratorFactory class implementation.
  //
  
  GenericSampleGeneratorFactory::GenericSampleGeneratorFactory(
      const Frame&            frame,
      ISampleRendererFactory* sample_renderer_factory,
      const ParamArray&       params)
    : m_frame(frame)
    , m_sample_renderer_factory(sample_renderer_factory)
    , m_params(params)
  {
  }
  
  void GenericSampleGeneratorFactory::release()
  {
      delete this;
  }
  
  ISampleGenerator* GenericSampleGeneratorFactory::create(
      const size_t            generator_index,
      const size_t            generator_count)
  {
      return
          new GenericSampleGenerator(
              m_frame,
              m_sample_renderer_factory,
              m_params,
              generator_index,
              generator_count);
  }
  
  SampleAccumulationBuffer* GenericSampleGeneratorFactory::create_sample_accumulation_buffer()
  {
      const CanvasProperties& props = m_frame.image().properties();
  
      return
          new LocalSampleAccumulationBuffer(
              props.m_canvas_width,
              props.m_canvas_height);
  }
  
  }   // namespace renderer
  